Below-average sea surface temperatures (SSTs) continued across the central and eastern equatorial Pacific Ocean during September [Fig. 1]. Most of the Niño indices decreased during the past month, with the latest weekly index values spanning -0.8°C to -1.6°C [Fig. 2]. For the last couple of months, negative subsurface temperature anomalies remained mostly unchanged [Fig. 3], reflecting the persistence of below-average temperatures across the eastern Pacific Ocean [Fig. 4]. Low-level easterly wind anomalies and upper-level westerly wind anomalies prevailed across most of the equatorial Pacific. Convection was suppressed over the western and central tropical Pacific and was enhanced over Indonesia [Fig. 5]. Overall, the coupled ocean-atmosphere system continued to reflect La Niña.

The most recent IRI plume forecast of the Niño-3.4 SST index indicates La Niña will persist into the Northern Hemisphere winter 2022-23, and then transition to ENSO-neutral in January-March 2023 [Fig. 6]. The forecaster consensus for this month favors a slightly later transition to ENSO-neutral, during February-April 2023, which is consistent with the latest North American Multi-Model Ensemble (NMME). However, predicting the timing of transitions is challenging, and there continues to be uncertainty over how long La Niña may last. In summary, there is a 75% chance of La Niña during the Northern Hemisphere winter (December-February) 2022-23, with a 54% chance for ENSO-neutral in February-April 2023 [Fig. 7].

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA's National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Additional perspectives and analysis are also available in an ENSO blog. A probabilistic strength forecast is available here. The next ENSO Diagnostics Discussion is scheduled for 10 November 2022.

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